Process for producing rubber composition

ABSTRACT

Process for producing a rubber composition comprising a rubber component (A) comprising at least one selected from natural rubbers and synthetic diene rubbers, a filler containing an inorganic filler (B), a silane coupling agent (C), and at least two kinds of chemical agents (D) and (E) selected from guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas, and xanthates, wherein the rubber composition is kneaded in a plurality of stages wherein, in the first stage (X) of kneading, the rubber component (A), all or a portion of the inorganic filler (B), all or a portion of the silane coupling agent (C), and at least two kinds of the chemical agents (D) and (E) are added and kneaded.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a National Stage of International Application No.PCT/JP2012/059591 filed Apr. 6, 2012, claiming priority based onJapanese Patent Application No. 2011-084934 filed Apr. 6, 2011, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a method for producing a rubbercomposition containing an inorganic filler and having an improvedlow-heat-generation property.

BACKGROUND ART

Recently, in association with the movement of global regulation ofcarbon dioxide emission associated with the increase in attraction toenvironmental concerns, the demand for low fuel consumption byautomobiles is increasing. To satisfy the requirement, it is desired toreduce rolling resistance relating to tire performance. Heretofore, as ameans for reducing the rolling resistance of tires, a method ofoptimizing tire structures has been investigated; however, at present, atechnique of using a low-heat-generating rubber composition for tireshas become employed as the most common method.

For obtaining such a low-heat-generating rubber composition, there isknown a method of sing an inorganic filler such as silica or the like.

However, in incorporating an inorganic filler such as silica or the likein a rubber composition to prepare an inorganic filler-containing rubbercomposition, the inorganic filler, especially silica aggregates in therubber composition (owing to the hydroxyl group in the surface ofsilica), and therefore, for preventing the aggregation, a silanecoupling agent is used.

Accordingly, for successfully solving the above-mentioned problem byincorporation of a silane coupling agent, various trials have been madefor increasing the activity of the coupling function of the silanecoupling agent.

For example, Patent Reference 1 proposes a rubber compositioncontaining, as basic components, at least (i) one diene elastomer, (ii)a white filler as a reinforcing filler and (iii) an alkoxysilanepolysulfide as a coupling agent (white filler/diene elastomer) alongwith (iv) an enamine and (v) a guanidine derivative.

Patent Reference 2 discloses a rubber composition containing, as basiccomponents, at least (i) one diene elastomer, (ii) a white filler as areinforcing filler and (iii) an alkoxysilane polysulfide as a couplingagent (white filler/diene elastomer) along with (iv) zinc thiophosphateand (v) a guanidine derivative.

Patent Reference 3 describes a rubber composition containing, as basiccomponents, at least (i) a diene elastomer, (ii) an inorganic filler asa reinforcing filler and (iii) an alkoxysilane polysulfide (PSAS) as an(inorganic filler/diene elastomer) coupling agent, as combined with (iv)an aldimine (R—CH═N—R) and (v) a guanidine derivative.

Further, Patent Reference 4 proposes a rubber composition basicallycontaining at least (i) a diene elastomer, (ii) an inorganic filer as areinforcing filer and (iii) an alkoxysilane polysulfide as a couplingagent, as combined with (iv) 1,2-dihydropyridine and (v) a guanidinederivative.

However, in these inventions, nothing is taken into considerationrelating to kneading conditions.

Furthermore, although Patent Reference 5 may be cited as an example ofimproving the coupling function activity of the silane coupling agentwith kneading conditions in consideration, further enhancement of theeffect of improving the coupling function activity of the silanecoupling agent is desired.

CITATION LIST Patent References

-   [Patent Reference 1] JP-T 2002-521515-   [Patent Reference 2] JP-T 2002-521516-   [Patent Reference 3] JP-T 2003-530443-   [Patent Reference 4] JP-T 2003-523472-   [Patent Reference 5] WO2008/123306

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

Under such circumstances, the object of the present invention is toprovide a process for producing a rubber composition, which enables asuitably low heat-generating rubber composition to be obtained byfurther improving the coupling function activity of the silane couplingagent.

Means for Solving the Problems

In order to accomplish the above object, the present inventors examinedvarious kneading methods in a process for producing a rubbercomposition, wherein, in the first or a subsequent stage of the kneadingprocess, a rubber component, all or a portion of an inorganic filler,all or a portion of the silane coupling agent, and at least two kinds ofchemical agents (chemical agents used ordinarily as vulcanizationaccelerators) are kneaded. As a result, it was found that improvement ofthe coupling function activity can be obtained by adjusting the stage ofkneading where at least two kinds of the accelerators are added. Thisfinding led to completion of the present invention.

That is, the present invention provides:

-   [1] a process for producing a rubber composition comprising a rubber    component (A) comprising at least one selected from natural rubbers    and synthetic diene rubbers, a filler containing an inorganic filler    (B), a silane coupling agent (C), and at least two kinds of chemical    agents (D) and (E) selected from guanidines, sulfenamides,    thiazoles, thiurams, dithiocarbamates, thioureas, and xanthates,    wherein the rubber composition is kneaded in a plurality of stages    wherein, in the first stage (X) of kneading, the rubber component    (A), all or a portion of the inorganic filler (B), all or a portion    of the silane coupling agent (C), and two of the chemical agents (D)    and (E) are added and kneaded;-   [2] the process for producing a rubber composition according to the    above [1], wherein, in the first stage (X) of kneading, the rubber    component (A), all or a portion of the inorganic filler (B), and all    or a portion of the silane coupling agent (C) are kneaded and    thereafter, during the first stage (X), at least two kinds of the    chemical agents (D) and (E) are added and kneaded further;-   [3] a process for producing a rubber composition comprising a rubber    component (A) comprising at least one selected from natural rubbers    and synthetic diene rubbers, a filler containing an inorganic filler    (B), a silane coupling agent (C), and at least two kinds of chemical    agents (D) and (E) selected from guanidines, sulfenamides,    thiazoles, thiurams, dithiocarbamates, thioureas, and xanthates,    wherein the rubber composition is kneaded in a kneading step    comprising three or more stages wherein, in the first stage (X) of    kneading, the rubber component (A), all or a portion of the    inorganic filler (B), and all or a portion of the silane coupling    agent (C) are kneaded; in a stage (Y) after the first stage but    before the last stage of kneading, at least two kinds of the    chemical agents (D) and (E) are added and kneaded; and, in the last    stage (Z) of kneading, a vulcanizing agent is added and kneaded;-   [4] a rubber composition produced by a process according to any of    the above [1] to [3]; and-   [5] a tire comprising the rubber composition according to the above    [4].

Advantage of the Invention

According to the present invention, there can be provided processes forproducing a rubber composition, which enable a rubber composition havingan excellent low heat-generating property to be obtained by furtherimproving the coupling function activity of the silane coupling agent.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the first and the second inventions of the presentinvention will be explained in detail. When an explanation common tothese first and second inventions is made, the inventions will bereferred to as “the present invention,” while when each of the first andsecond inventions is explained separately, the invention will bereferred to as “the first invention” or as “the second invention.”

In the present invention, the reason why the rubber component, all or aportion of the inorganic filler (B), all or a portion of the silanecoupling agent (C) are kneaded in the first stage (X) of kneading is tomake the reaction of the inorganic filler (B) and the silane couplingagent (C) proceed sufficiently.

The first stage of kneading (X) in the present invention is the firststage of kneading the rubber component (A), the inorganic filler (B) andthe silane coupling agent (C), but does not include a case of kneadingthe rubber component (A) and the other filler than the inorganic filler(B) in the initial stage and a case of pre-kneading the rubber component(A) alone.

The first invention is a process for producing a rubber compositioncomprising a rubber component (A) comprising at least one selected fromnatural rubbers and synthetic diene rubbers, a filler containing aninorganic filler (B), a silane coupling agent (C), and at least twokinds of chemical agents (D) and (E) selected from guanidines,sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas, andxanthates, wherein the rubber composition is kneaded in a plurality ofstages wherein, in the first stage (X) of kneading, the rubber component(A), all or a portion of the inorganic filler (B), all or a portion ofthe silane coupling agent (C), and at least two kinds of the chemicalagents (D) and (E) are added and kneaded.

In the first invention, the reason why at least two kinds of chemicalagents (D) and (E) are added and kneaded in the first stage (X) ofkneading is to improve more suitably the coupling function activity ofthe silane coupling agent (C).

The chemical agents (D) and (E) are at least two selected fromguanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates,thioureas, and xanthates. This is so because these can improvereactivity of the silane coupling agents (C) significantly.

In the first invention, it is preferable that, in the first stage (X) ofkneading, the rubber component (A), all or a portion of the inorganicfiller (B), and all or a portion of the silane coupling agent (C), arekneaded and, thereafter, during the first stage (X), at least two kindsof the chemical agents (D) and (E) are added and kneaded further, whichis a preferred embodiment.

The reason why at least two kinds of the chemical agents (D) and (E) areadded during the first stage (X) of kneading is because the reaction ofthe silane coupling agent (C) and the rubber component (A) can be madeto proceed after the inorganic filler (B) and the silane coupling agent(C) proceeded sufficiently and, thus, the coupling function activity ofthe silane coupling agent (C) can be further improved.

In the above embodiment of the first invention, the time after additionof the rubber component (A), all or a portion of the inorganic filler(B), and all or a portion of the silane coupling agent (C) untiladdition of the chemical agent (D) during the first stage is preferably10 to 180 seconds. The lower limit of this time is more preferably 30seconds or more; and the upper limit is more preferably 150 seconds orless, even more preferably 120 seconds or less. When this time is 10seconds or more, the reaction of (B) and (C) can proceed sufficiently.Even if this time exceeded 180 seconds, the reaction of (B) and (C) hadalready proceeded sufficiently and no further effect can be acquired;and, when this time is 180 seconds or less, the unvulcanized viscositydoes not become too high. Thus, the upper limit is preferably set to 180seconds.

Further, in the above embodiment of the first invention, in order tomore suitably improve the coupling function activity of the silanecoupling agent (C), it is preferable, in the first stage of kneading, toadd the at least two kinds of chemical agents (D) and (E) whentemperature of the rubber composition reached 125 to 180° C.

Hereinafter, addition of the chemical agents during the first stage (X)may sometimes be referred to as “delayed addition of the chemical agentsduring the first stage (X).”

The second invention is a process for producing a rubber compositioncomprising a rubber component (A) comprising at least one selected fromnatural rubbers and synthetic diene rubbers, a filler containing aninorganic filler (B), a silane coupling agent (C), and at least twokinds of chemical agents (D) and (E) selected from guanidines,sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas, andxanthates, wherein the rubber composition is kneaded in a kneading stepcomprising three or more stages, wherein, in the first stage (X) ofkneading, the rubber component (A), all or a portion of the inorganicfiller (B), and all or a portion of the silane coupling agent (C) arekneaded; in a stage (Y) after the first stage and before the last stageof kneading, at least two kinds of the chemical agents (D) and (E) areadded and kneaded; and, in the last stage (Z) of kneading, a vulcanizingagent is added and kneaded.

The kneading process of the rubber composition in the second inventionincludes at least the first stage (X) of kneading, a stage (Y) after thefirst stage but before the last stage of kneading, and the last stage(Z) of kneading. If necessary, other intermediate stages of kneading maybe included.

The kneading step in the production process of the present inventionsuffices if it comprises three or more stages. The number of stages ofkneading is not particularly limited but when productivity isconsidered, it comprises preferably eight or less stages, morepreferably six or less stages, and even more preferably four or lessstages.

In the second invention, the reason why kneading is carried out by akneading step comprising three or more stages is in order to suppressdecrease in molecular weight of the rubber component (A) due to kneadingat high temperature for a long time. That is, if the time of onekneading stage is made longer in order to decrease the number of stagesof kneading, the rubber component (A) becomes exposed to hightemperature for a long time and results in a possible decrease in themolecular weight thereof. It is important to avoid this.

Furthermore, in the second invention, the reason why at least two kindsof chemical agents (D) and (E) are added and kneaded in a stage (Y)after the first stage but before the last stage of kneading is because,after a reaction of the inorganic filler (B) and the silane couplingagent (C) proceeded sufficiently, the coupling function activity of thesilane coupling agent (C) is improved by the chemical agents (D) and (E)and a reaction of the silane coupling agent (C) and a rubber component(A) can be made to proceed more suitably. In order to enable thereaction of the silane coupling agent (C) and the rubber component (A)to proceed even more suitably, the maximum temperature of the rubbercomposition in the stage (Y) of kneading is preferably 120 to 190° C.,more preferably 120 to 175° C., and even more preferably 130 to 175° C.

In the present invention, in order to enable the reaction of the silanecoupling agent (C) and the rubber component (A) to proceed even moresuitably by more suitably improving the coupling function activity ofthe above silane coupling agent (C), the maximum temperature of therubber composition in the first stage (X) is preferably 120 to 190° C.,more preferably 120 to 175° C., and especially preferably 130 to 175° C.

[Silane Coupling Agent (C)]

The silane coupling agent (C) used in the process for producing a rubbercomposition of the present invention is preferably one or more compoundsselected from the group consisting of the compounds represented by thefollowing general formulae (I) to (IV).

Using the silane coupling agent (C) of the type, the rubber compositionin the present invention is excellent in workability thereof and cangive pneumatic tires having good abrasion resistance.

General formulae (I) and (IV) are sequentially described below.

[Chemical Formula 1](R¹O)_(3−p)(R²)_(p)Si—R³—S_(a)—R³—Si(OR¹)_(3−r)(R²)_(r)  (I)

In the formula, R¹'s may be the same or different and are each a linear,cyclic, or branched alkyl group, having 1 to 8 carbon atoms, or a linearor branched alkoxyalkyl group having 2 to 8 carbon atoms; R²'s may bethe same or different and are each a linear, cyclic, or branched alkylgroup, having 1 to 8 carbon atoms; R³'s may be the same or different andare each a linear or branched alkylene group, having 1 to 8 carbonatoms; a is 2 to 6 as an average value; and p and q may be the same ordifferent and are each 0 to 3 as an average value, provided that p and rare not 3 at the same time.

Specific examples of the silane coupling agent (C) represented by theabove-mentioned general formula (I) includebis(3-triethoxysilylpropyl)tetrasulfide,bis(3-trimethoxysilylpropyl)tetrasulfide,bis(3-methyldimethoxysilylpropyl)tetrasulfide,bis(2-triethoxysilylethyl)tetrasulfide,bis(3-triethoxysilylpropyl)disulfide,bis(3-trimethoxysilylpropyl)disulfide,bis(3-methyldimethoxysilylpropyl)disulfide,bis(2-triethoxysilylethyl)disulfide,bis(3-triethoxysilylpropyl)trisulfide,bis(3-trimethoxysilylpropyl)trisulfide,bis(3-methyldimethoxysilylpropyl)trisulfide,bis(2-triethoxysilylethyl)trisulfide,bis(3-monoethoxydimethylsilylpropyl)tetrasulfide,bis(3-monoethoxydimethylsilylpropyl)trisulfide,bis(3-monoethoxydimethylsilylpropyl)disulfide,bis(3-monomethoxydimethylsilylpropyl)tetrasulfide,bis(3-monomethoxydimethylsilylpropyl)trisulfide,bis(3-monomethoxydimethylsilylpropyl)disulfide,bis(2-monoethoxydimethylsilylethyl)tetrasulfide,bis(2-monoethoxydimethylsilylethyl)trisulfide,bis(2-monoethoxydimethylsilylethyl)disulfide.

In the formula, R⁴ is a monovalent group selected from —Cl, —Br, R⁹O—,R⁹(C═O)O—, R⁹R¹⁰C═NO—, R⁹R¹⁰CNO—, R⁹R¹⁰N—, and—(OSiR⁹R¹⁰)_(h)(OSiR⁹R¹⁰R¹¹) (R⁹, R¹⁰, and R¹¹ may be the same ordifferent and are each a hydrogen atom or a monovalent hydrocarbon grouphaving 1 to 18 carbon atoms); R⁵ represents R⁴, a hydrogen atom, or amonovalent hydrocarbon group having 1 to 18 carbon atoms; R⁶ representsR⁴, R⁵, a hydrogen atom, or a —[O(R¹²O)_(j)]_(0.5)— group (R¹² is analkylene group having 1 to 18 carbon atoms and j is an integer from 1 to4); R⁷ represents a divalent hydrocarbon group having 1 to 18 carbonatoms; R⁸ represents a monovalent hydrocarbon group having 1 to 18carbon atoms; and x, y, and z are numbers which satisfy therelationships: x+y+2z=3, 0≦x≦3, 0≦y≦2, and 0≦z≦1.

In the above general formula (II), R⁸, R⁹, R¹⁰, and R¹¹ may be the sameor different and are each preferably a group selected from the groupconsisting of a linear, cyclic, or a branched alkyl group, an alkenylgroup, an aryl group, and an aralkyl group, each having 1 to 18 carbonatoms. In addition, when R⁵ is a monovalent hydrocarbon group having 1to 18 carbon atoms, it is preferably a group selected from a linear,cyclic, or branched alkyl group, an alkenyl group, an aryl group, and anaralkyl group; R¹² is preferably a linear, cyclic, or branched alkylenegroup, especially a branched one; R⁷ includes, for example, an aklylenegroup having 1 to 18 carbon atoms, an alkenylene group having 2 to 18carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, acycloalkylalkylene group having 6 to 18 carbon atoms, an arylene grouphaving 6 to 18 carbon atoms, and an aralkylene group having 7 to 18carbon atoms. The alkylene group and the alkenylene group may be eitherlinear or branched; and the cycloalkylene group, the cycloalkylalkylenegroup, the arylene group, and the aralkylene group may have asubstituent such as a lower alkyl group and the like on the ring. Asthis R⁷, preferable is an alkylene group having 1 to 6 carbon atoms andthere may especially preferably be mentioned a linear alkylene group,for example, a methylene group, an ethylene group, a trimethylene group,a tetramethylene group, a pentamethylene group, and a hexamethylenegroup.

In the above general formula (II), specific examples of the monovalenthydrocarbon groups having 1 to 18 carbon atoms of R⁵, R⁸, R⁹, R¹⁰, andR¹¹ include a methyl group, an ethyl group, a n-propyl group, anisopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group,a tert-butyl group, a pentyl group, a hexyl group, an octyl group, adecyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, avinyl group, a propenyl group, an allyl group, a hexenyl group, anoctenyl group, a cyclopentenyl group, a cyclohexenyl group, a phenylgroup, a tolyl group, a xylyl group, a naphthyl group, a benzyl group, aphenethyl group, a naphthylmethyl group, and the like.

In the general formula (II), examples of R¹² include a methylene group,an ethylene group, a trimethylene group, a tetramethylene group, apentamethylene group, a hexamethylene group, an octamethylene group, adecamethylene group, a dodecamethylene group, and the like.

Specific examples of the silane coupling agent represented by thegeneral formula (II) include 3-hexanoylthiopropyltriethoxysilane,3-octanoylthiopropyltriethoxysilane,3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane,2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane,2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane,3-hexanoylthiopropyltrimethoxysilane,3-octanoylthiopropyltrimethoxysilane,3-decanoylthiopropyltrimethoxysilane,3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane,2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane,and the like. Among these, 3-octanoylthiopropyltriethoxysilane [tradename “NXT Silane” (registered trademark) produced by MomentivePerformance Materials Inc.] is especially preferable

[Chemical Formula 3](R¹³O)_(3−s)(R¹⁴)_(s)Si—R¹⁵—S_(k)—R¹⁶—S_(k)—R¹⁵—Si(OR¹³)_(3−t)(R¹⁴)_(t)  (III)

In the formula, R¹³'s may be the same or different and are each alinear, cyclic, or branched alkyl group, having 1 to 8 carbon atoms, ora linear or branched alkoxyalkyl group having 2 to 8 carbon atoms; R¹⁴'smay be the same or different and are each a linear, cyclic, or branchedalkyl group, having 1 to 8 carbon atoms; R¹⁵'s may be the same ordifferent and are each a linear or branched alkylene group, having 1 to8 carbon atoms; R¹⁶ is a divalent group of any of general formulae,(—S—R¹⁷—S—), (—R¹⁸—S_(m1)—R¹⁹—), and (—R₂₀—S_(m2)—R²¹—S_(m3)—R²²—) (R¹⁷to R²² may be the same or different and are each a divalent hydrocarbongroup, a divalent aromatic group or a divalent organic group containinga heteroatom other than sulfur and oxygen, each having 1 to 20 carbonatoms; and m1, m2, and m3 may be the same or different and are each 1 ormore but less than 4 as an average value); k's may be the same ordifferent and are each 1 to 6 as an average value; s and t may be thesame or different and are each 0 to 3 as an average value, provided thats and t are not 3 at the same time.

Preferred examples of the silane coupling agent (C) represented by theabove-mentioned general formula (III) are compounds represented by anaverage compositional formula(CH₃CH₂O)₃Si—(CH₂)₃—S₂—(CH₂)₆—S₂—(CH₂)₃—Si(OCH₂CH₃)₃,

-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S₂—(CH₂)₁₀—S₂—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S₃—(CH₂)₆—S₃—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S₄—(CH₂)₆—S₄—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(2.5)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S₃—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S₄—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₁₀—S₂—(CH₂)₁₀—S—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S₄—(CH₂)₆—S₄—(CH₂)₆—S₄—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S₂—(CH₂)₆—S₂—(CH₂)₆—S₂—(CH₂)₃—Si(OCH₂CH₃)₃,-   an average compositional formula    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃,    etc.

In the formula, R²³ is a linear, branched, or cyclic alkyl group, having1 to 20 carbon atoms; G's may be the same or different and are each analkanediyl group or an alkenediyl group, having 1 to 9 carbon atoms;Z^(a)'s may be the same or different and are each a group which can bondto two silicon atoms and is selected from [—O—]_(0.5), [—O-G-]_(0.5), or[—O-G-O—]_(0.5); Z^(b)'s may be the same or different and are each agroup which can bond to two silicon atoms and is a functional grouprepresented by [—O-G-O—]_(0.5); Z^(c)'s may be the same or different andare each a functional group represented by —Cl, —Br, —OR^(a),R^(a)C(═O)O—, R^(a)R^(b)C═NO—, R^(a)R^(b)N—, R^(a)—, HO-G-O— (G is thesame as the above description); R^(a) and R^(b) may be the same ordifferent and are each a linear, branched, or cyclic alkyl group, having1 to 20 carbon atoms; and m, n, u, v, and w may be the same or differentand 1≦m≦20, 0≦n≦20, 0≦u≦3, 0≦v≦2, 0≦w≦1, and (u/2)+v+2w=2 or 3; when theA portion exists in plurality, Z^(a) _(u)'s, Z^(b) _(v)'s, and Z^(c)_(w)'s in the plural A portions may each be the same or different; and,when the B portion exists in plurality, Z^(a) _(u)'s, Z^(b) _(v)'s, andZ^(c) _(w)'s in the plural B portions may each be the same or different.

Specific examples of the silane coupling agent represented by thegeneral formula (IV) include those represented by chemical formula (V),chemical formula (VI), and chemical formula (VII).

In the formula, L's are each independently an alkanediyl group or analkenediyl group having 1 to 9 carbon atoms; x=m; and y=n.

As a silane coupling agent represented by the chemical formula (V),there can be obtained commercially “NXT Low-V Silane” (trademark)produced by Momentive Performance Materials, Inc.

Furthermore, as a silane coupling agent represented by the chemicalformula (VI), there can similarly be obtained commercially “NXT UltraLow-V Silane” (trademark) produced by Momentive Performance Materials,Inc.

Further, as a silane coupling agent represented by the chemical formula(VII), there can be mentioned “NXT-Z” (trademark) produced by MomentivePerformance Materials, Inc.

Because the above silane coupling agents represented by the generalformula (II), the chemical formula (V), and the chemical formula (VI)possess protected mercapto groups, occurrence of initial vulcanization(scorch) during fabrication in processes before vulcanization can beprevented, resulting in good workability.

Furthermore, because, in the silane coupling agents represented by thechemical formulae (V), (VI), and (VII), the alkoxy silane groups havemany carbon atoms, there is little generation of volatile organiccompounds, VOC (especially alcohols), which is preferable in terms ofwork environments. Also, the coupling agent represented by the chemicalformula (VII) is more preferable because it enables a lowheat-generating property to be obtained as tire performance.

The silane coupling agent (C) involved in the present invention isespecially preferably a compound represented by the general formula (I)among the compounds represented by the above general formulae (I) to(IV). This is so because the chemical agent (D) easily activates thepolysulfide bond portion which reacts with the rubber component (A).

In the present invention, the silane coupling agent (C) may be usedsingly or in a combination of two or more.

The amount of the silane coupling agent (C) blended in the rubbercomposition of the present invention is preferably 1 to 20 mass %relative to the inorganic filler. This is so because, when the amount isless than 1 mass %, the effect of improving the low heat-generatingproperty of the rubber composition becomes difficult to be displayedand, when the amount exceeds 20 mass %, the cost of the rubbercomposition becomes excessive and economic efficiency deteriorates.Furthermore, the amount is more preferably 3 to 20 mass % relative tothe inorganic filler and especially preferably 4 to 10 mass % relativeto the inorganic filler.

[Chemical Agents, (D) and (E)]

The guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates,thioureas, and xanthates which are cited as the chemical agents (D) and(E) used in the process for producing a rubber composition of thepresent invention will be described in detail.

Additionally, in the present invention, the chemical agents (D) and (E)are used also as vulcanization accelerators in sulfur vulcanization andmay be blended in adequate amounts in the last stage of kneading, ifdesired.

In the present invention, the vulcanization accelerator added in thefirst stage (X) of kneading and/or in a stage (Y) before the last stageof kneading is referred to as the chemical agent in order to distinguishthem from the vulcanization accelerator which is added in the last stageof kneading together with a vulcanizing agent such as sulfur and thelike.

The guanidines used in the process for producing a rubber composition ofthe present invention include 1,3-diphenylguanidine,1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt ofdicatechol borate, 1,3-di-o-cumenylguanidine,1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, andthe like. Among these, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine,and 1-o-tolylbiguanide are preferable because these are highly reactive.

The sulfenamides used in the process for producing a rubber compositionof the present invention includeN-cyclohexyl-2-benzothiazolylsulfenamide,N,N-dicyclohexyl-2-benzothiazolylsulfenamide,N-tert-butyl-2-benzothiazolylsulfenamide,N-oxydiethylene-2-benzothiazolylsulfenamide,N-methyl-2-benzothiazolylsulfenamide,N-ethyl-2-benzothiazolylsulfenamide,N-propyl-2-benzothiazolylsulfenamide,N-butyl-2-benzothiazolylsulfenamide,N-pentyl-2-benzothiazolylsulfenamide,N-hexyl-2-benzothiazolylsulfenamide,N-pentyl-2-benzothiazolylsulfenamide,N-octyl-2-benzothiazolylsulfenamide,N-2-ethylhexyl-2-benzothiazolylsulfenamide,N-decyl-2-benzothiazolylsulfenamide,N-dodecyl-2-benzothiazolylsulfenamide,N-stearyl-2-benzothiazolylsulfenamide,N,N-dimethyl-2-benzothiazolylsulfenamide,N,N-diethyl-2-benzothiazolylsulfenamide,N,N-dipropyl-2-benzothiazolylsulfenamide,N,N-dibutyl-2-benzothiazolylsulfenamide,N,N-dipentyl-2-benzothiazolylsulfenamide,N,N-dihexyl-2-benzothiazolylsulfenamide,N,N-dipentyl-2-benzothiazolylsulfenamide,N,N-dioctyl-2-benzothiazolylsulfenamide,N,N-di-2-ethylhexylbenzothiazolylsulfenamide,N-decyl-2-benzothiazolylsulfenamide,N,N-didodecyl-2-benzothiazolylsulfenamide,N,N-distearyl-2-benzothiazolylsulfenamide, and the like. Among these,N-cyclohexyl-2-benzothiazolylsulfenamide andN-tert-butyl-2-benzothiazolylsulfenamide are preferable because they arehighly reactive.

The thiazoles used in the process for producing a rubber composition ofthe present invention include 2-mercaptobenzothiazole,di-2-benzothiazolyl disulfide, 2-mercaptobenzothiazole zinc salt,2-mercaptobenzothiazole cyclohexylamine salt,2-(N,N-diethylthiocarbamoylthio)benzothiazole,2-(4′-morpholinodithio)benzothiazole, 4-methyl-2-mercaptobenzothiazole,di-(4-methyl-2-benzothiazolyl)disulfide,5-chloro-2-mercaptobenzothiazole, 2-mercaptobenzothiazole sodium salt,2-mercapto-6-nitrobenzothiazole, 2-mercaptonaphtho[1,2-d]thiazole,2-mercapto-5-methoxybenzothiazole, 6-amino-2-mercaptobenzothiazole, andthe like. Among these, 2-mercaptobenzothiazole and di-2-benzothiazolyldisulfide are preferable because they are highly reactive.

The thiurams used in the process for producing a rubber composition ofthe present invention include tetramethylthiuram disulfide,tetraethylthiuram disulfide, tetrapropylthiuram disulfide,tetraisopropylthiuram disulfide, tetrabutylthiuram disulfide,tetrapentylthiuram disulfide, tetrahexylthiuram disulfide,tetraheptylthiuram disulfide, tetraoctylthiuram disulfide,tetranonylthiuram disulfide, tetradecylthiuram disulfide,tetradodecylthiuram disulfide, tetrastearylthiuram disulfide,tetrabenzylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide,tetramethylthiuram monosulfide, tetraethylthiuram monosulfide,tetrapropylthiuram monosulfide, tetraisopropylthiuram monosulfide,tetrabutylthiuram monosulfide, tetrapentylthiuram monosulfide,tetrahexylthiuram monosulfide, tetraheptylthiuram monosulfide,tetraoctylthiuram monoisulfide, tetranonylthiuram monosulfide,tetradecylthiuram monosulfide, tetra dodecylthiuram monosulfide,tetrastearylthiuram monosulfide, tetrabenzylthiuram monosulfide,dipentamethylenethiuram tetrasulfide, and the like. Among these,tetrakis(2-ethylhexyl)thiuram disulfide and tetrabenzylthiuram disulfideare preferable because these are highly reactive.

The thioureas used in the process for producing a rubber composition ofthe present invention include N,N′-diphenylthiourea, trimethylthiourea,N,N′-diethylthiourea, N,N′-dimethylthiourea, N,N′-dibutylthiourea,ethylenethiourea, N,N′-diisopropylthiourea, N,N′-dicyclohexylthiourea,1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea,1,1-diphenyl-2-thiourea, 2,5-dithiobiurea, guanylthiourea,1-(1-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea,o-tolylthiourea, and the like. Among these, N,N′-diethylthiourea,tolylmethylthiourea, N,N′-diphenylthiourea, and N,N′-dimethylthioureaare preferable because these are highly reactive.

The dithiocarbamates used in the process for producing a rubbercomposition of the present invention include zincdimethyldithiocarbamate, zinc diethyldithiocarbamate, zincdipropyldithiocarbamate, zinc diisopropyldithiocarbamate, zincdibutyldithiocarbamate, zinc dipentyldithiocarbamate, zincdihexyldithiocarbamate, zinc diheptyldithiocarbamate, zincdioctyldithiocarbamate, zinc di(2-ethylhexyl)dithiocarbamate, zincdidecyldithiocarbamate, zinc didodecyldithiocarbamate, zincN-pentamethylenedithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate,zinc dibenzyldithiocarbamate, copper dimethyldithiocarbamate, copperdiethyldithiocarbamate, copper dipropyldithiocarbamate, copperdiisopropyldithiocarbamate, copper dibutyldithiocarbamate, copperdipentyldithiocarbamate, copper dihexyldithiocarbamate, copperdiheptyldithiocarbamate, copper dioctyldithiocarbamate, copperdi(2-ethylhexyl)dithiocarbamate, copper didecyldithiocarbamate, copperdidodecyldithiocarbamate, copper N-pentamethylenedithiocarbamate, copperdibenzyldithiocarbamate, sodium dimethyldithiocarbamate, sodiumdiethyldithiocarbamate, sodium dipropyldithiocarbamate, sodiumdiisopropyldithiocarbamate, sodium dibutyldithiocarbamate, sodiumdipentyldithiocarbamate, sodium dihexyldithiocarbamate, sodiumdiheptyldithiocarbamate, sodium dioctyldithiocarbamate, sodiumdi(2-ethylhexyl)dithiocarbamate, sodium didecyldithiocarbamate, sodiumdidodecyldithiocarbamate, sodium N-pentamethylenedithiocarbamate, sodiumdibenzyldithiocarbamate, ferric dimethyldithiocarbamate, ferricdiethyldithiocarbamate, ferric dipropyldithiocarbamate, ferricdiisopropyldithiocarbamate, ferric dibutyldithiocarbamate, ferricdipentyldithiocarbamate, ferric dihexyldithiocarbamate, ferricdiheptyldithiocarbamate, ferric dioctyldithiocarbamate, ferricdi(2-ethylhexyl)dithiocarbamate, ferric didecyldithiocarbamate, ferricdidodecyldithiocarbamate, ferric N-pentamethylenedithiocarbamate, ferricdibenzyldithiocarbamate, and the like. Among these, zincdibenzyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zincdimethyldithiocarbamate, and copper dimethyldithiocarbamate arepreferable because these are highly reactive.

The xanthates used in the process for producing a rubber composition ofthe present invention include zinc methyl xanthate, zinc ethyl xanthate,zinc propyl xanthate, zinc isopropyl xanthate, zinc butyl xanthate, zincpentyl xanthate, zinc hexyl xanthate, zinc heptyl xanthate, zinc octylxanthate, zinc 2-ethylhexyl xanthate, zinc decyl xanthate, zinc dodecylxanthate, potassium methyl xanthate, potassium ethyl xanthate, potassiumpropyl xanthate, potassium isopropyl xanthate, potassium butyl xanthate,potassium pentyl xanthate, potassium hexyl xanthate, potassium heptylxanthate, potassium octyl xanthate, potassium 2-ethylhexyl xanthate,potassium decyl xanthate, potassium dodecyl xanthate, sodium methylxanthate, sodium ethyl xanthate, sodium propyl xanthate, sodiumisopropyl xanthate, sodium butyl xanthate, sodium pentyl xanthate,sodium hexyl xanthate, sodium heptyl xanthate, sodium octyl xanthate,sodium 2-ethylhexyl xanthate, sodium decyl xanthate, sodium dodecylxanthate, and the like. Among these, zinc isopropyl xanthate ispreferable because it is highly reactive.

[Rubber Component (A)]

As the synthetic dienic rubber of the rubber component (A) for use inthe rubber composition production method of the present invention,usable here are styrene-butadiene copolymer rubber (SBR), polybutadienerubber (BR), polyisoprene rubber (IR), butyl rubber (IIR),ethylene-propylene-diene tercopolymer rubber (EPDM), etc. One or moredifferent types of natural rubbers and synthetic dienic rubbers may beused here either singly or as combined.

[Inorganic Filler (B)]

As the inorganic filler (B) for use in the rubber composition productionmethod of the present invention, usable are silica and an inorganiccompound represented by the following general formula (VIII):dM¹.xSiO_(y).zH₂O  (VIII)

In the general formula (VIII), M¹ represents at least one selected from,a metal selected from aluminium, magnesium, titanium, calcium andzirconium, and oxides or hydroxides of those metals, their hydrates, orcarbonates of the metals; d, x, y and z each indicate an integer of from1 to 5, an integer of from 0 to 10, an integer of from 2 to 5, and aninteger of from 0 to 10, respectively.

In the general formula (VIII), when x and z are both 0, then theinorganic compound is at least one metal selected from aluminium,magnesium, titanium, calcium and zirconium, or a metal oxide or metalhydroxide thereof.

In the present invention, silica is preferred as the inorganic filler(B) from the viewpoint of satisfying both low rolling property andabrasion resistance. As silica, any commercially-available one is usablehere; and above all, preferred is precipitated silica, fumed silica orcolloidal silica, and more preferred is precipitated silica. Preferably,the BET specific surface area (as measured according to ISO 5794/1) ofsilica for use herein is from 40 to 350 m²/g. Silica of which the BETspecific surface area falls within the range is advantageous in that itsatisfies both rubber-reinforcing capability and dispersibility inrubber component. From this viewpoint, silica having a BET specificsurface area in a range of 80 to 350 m²/g is more preferable, especiallypreferable being silica having a BET specific surface area in a range of120 to 350 m²/g. As such silica, there may be used commercial productssuch as trade name “Nipsil AQ” (BET specific surface area=220 m²/g) andtrade name “Nipsil KQ” produced by Tosoh Silica Corporation, and“Ultrasil VN3” (BET specific surface area=175 m²/g) produced by DegussaAG, and the like.

As the inorganic compound represented by the general formula (III),usable here are alumina (Al₂O₃) such as γ-alumina, α-alumina, etc.;alumina monohydrate (Al₂O₃.H₂O) such as boehmite, diaspore, etc.;aluminium hydroxide [Al(OH)₃] such as gypsite, bayerite, etc.; aluminiumcarbonate [Al₂(CO₃)₂], magnesium hydroxide [Mg(OH)₂], magnesium oxide(MgO), magnesium carbonate (MgCO₃), talc (3MgO.4SiO₂.H₂O), attapulgite(5MgO.8SiO₂.9H₂O), titanium white (TiO₂), titanium black (TiO_(2n-1)),calcium oxide (CaO), calcium hydroxide [Ca(OH)₂], aluminium magnesiumoxide (MgO.Al₂O₃), clay (Al₂O₃.2SiO₂), kaolin (Al₂O₃0.2SiO₂.2H₂O),pyrophyllite (Al₂O₃.4SiO₂.H₂O), bentonite (Al₂O₃.4SiO₂.2H₂O), aluminiumsilicate (Al₂SiO₅, Al₄.3SiO₄.5H₂O, etc.), magnesium silicate (Mg₂SiO₄,MgSiO₃, etc.), calcium silicate (Ca₂.SiO₄, etc.), aluminium calciumsilicate (Al₂O₃.Ca.2SiO₂, etc.), magnesium calcium silicate (CaMgSiO₄),calcium carbonate (CaCO₃), zirconium oxide (ZrO₂), zirconium hydroxide[ZrO(OH)₂.nH₂O], zirconium carbonate [Zr(CO₃)₂]; as well as crystallinealuminosilicate salts containing a charge-correcting hydrogen, alkalimetal or alkaline earth metal such as various types of zeolite. Also, itis preferable when M¹ in the general formula (VIII) is at least oneselected from an aluminum metal, an oxide or a hydroxide of aluminum ora hydrate thereof, or a carbonate of aluminum. Among these, aluminumhydroxide is especially preferable.

One or more different types of the inorganic compounds of the generalformula (VIII) may be used here either singly or as combined. The meanparticle size of the inorganic compound is preferably within a range offrom 0.01 to 10 μm from the viewpoint of the balance of kneadingworkability, abrasion resistance and wet grip performance, and morepreferably within a range of from 0.05 to 5 μm.

As the inorganic filler (B) in the present invention, silica alone maybe used, or silica as combined with at least one inorganic compound ofthe general formula (VIII) may be used.

If desired, the filler in the rubber composition in the presentinvention may contain carbon black in addition to the above-mentionedinorganic filler (B). Containing carbon black, the filler enjoys theeffect of lowering the electric resistance of the rubber composition tothereby prevent static electrification thereof. Carbon black for useherein is not specifically defined. For example, preferred is use ofhigh, middle or low-structure SAF, ISAF, IISAF, N339, HAF, FEF, GPF,SRF-grade carbon black; and more preferred is use of SAF, ISAF, IISAF,N339, HAF, FEF-grade carbon black. Preferably, the nitrogen adsorptionspecific surface area (N₂SA, as measured according to JIS K 6217-2:2001)of such carbon black is from 30 to 250 m²/g. One alone or two or moredifferent types of such carbon black may be used here either singly oras combined. In the present invention, the inorganic filler (B) does notcontain carbon black.

The inorganic filler (B) in the rubber composition in the presentinvention is preferably in an amount of from 20 to 120 parts by massrelative to 100 parts by mass of the rubber component (A). When theamount is at least 20 parts by mass, then it is favorable from theviewpoint of securing wet performance; and when at most 120 parts bymass, then it is favorable from the viewpoint of reducing rollingresistance. Further, the amount is more preferably from 30 to 100 partsby mass.

Also preferably, the filler in the rubber composition in the presentinvention is in an amount of from 20 to 150 parts by mass relative to100 parts by mass of the rubber component (A). When the amount is atleast 20 parts by mass, then it is favorable from the viewpoint ofenhancing rubber composition reinforcing capability; and when at most150 parts by mass, then it is favorable from the viewpoint of reducingrolling resistance.

Of the filler, the inorganic filler (B) accounts for, from the viewpointof a balance between the wet performance and the rolling resistance,preferably 40 mass % or more and more preferably 70 mass % or more.

[Organic Acid Compound (G)]

In the production process of the present invention, the number ofmolecules (number of moles) of the organic acid compound (G) containedin the rubber composition in the first stage (X) of kneading or a stage(Y) of kneading is preferably not more than the number of molecules(number of moles) of the agent (D) added in the first stage (X) or thestage (Y). This is in order to suitably suppress reduction of the effectof activity improvement, the reduction occurring when the number ofmolecules (number of moles) of the organic acid compound (G) is morethan the number of molecules (number of moles) of the chemical agents(D) and (E).

In the present invention, the organic acid compound (G) is preferablyadded in a stage of kneading after addition of the silane coupling agent(C) {that is, in the stage (Y) of kneading or the last stage (Z) ofkneading}. This is in order to further enhance the effect of improvingthe coupling activity, obtained by blending of the chemical agents (D)and (E).

The organic acid compound (G) blended in the rubber composition of thepresent invention includes organic acids such as saturated fatty acids,unsaturated fatty acids, resin acids such as rosin acids or modifiedrosin acids, and the like including stearic acid, palmitic acid,myristic acid, lauric acid, arachidic acid, behenic acid, lignocericacid, capric acid, pelargonic acid, caprylic acid, enanthic acid,caproic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid,nervonic acid, and the like; and alkali metal salts or esters of thesaturated fatty acids, the unsaturated fatty acids, and the resin acids.As the alkali metals, preferable are sodium, potassium, and the like.

In the present invention, 50 mol % or more of the organic acid compound(G) is preferably stearic acid because the compound has to sufficientlyexhibit its function as a vulcanization accelerating aid.

Further, when an emulsion-polymerized styrene-butadiene copolymer isused as a portion or all of the rubber component (A), it is preferable,from the viewpoint of an emulsifier necessary to obtain theemulsion-polymerized styrene-butadiene copolymer, that 50 mol % or moreof the organic acid compound is accounted for by the rosin acids(including the modified rosin acids) and/or fatty acids which arecontained in the emulsion-polymerized styrene-butadiene copolymer.

In the rubber composition production method of the present invention,various additives that are generally incorporated in a rubbercomposition, for example, a vulcanization activator such as zinc floweror the like, an antioxidant and others may be optionally added andkneaded in the first stage or the final stage of kneading, or in theintermediate stage between the first stage and the final stage.

As the kneading apparatus for the production method of the presentinvention, usable is any of a Banbury mixer, a roll, an intensive mixer,etc.

EXAMPLES

The present invention is described in more detail with reference to thefollowing Examples; however, the present invention is not limited at allby the following Examples.

Low-heat-generating property (tan δ index) was evaluated according tothe following method.

Low-Heat-Generation Property (tan δ Index)

Using a viscoelasticity measuring device (by Rheometric), tan δ of therubber composition sample was measured at a temperature of 60° C., at adynamic strain of 5% and at a frequency of 15 Hz. Taking the reciprocalof tan δ in Comparative Example 1, 10 or 17 as 100, the data wereexpressed as index indication according to the following formula. Thesamples having a larger index value have a better low-heat-generationproperty and have a smaller hysteresis loss.Low heat generation index={(tan δ of vulcanized rubber composition ofComparative Example 1)/(tan δ of vulcanized rubber compositiontested)}×100

Production Example 1 Production of Silane Coupling Agent Represented byAverage Compositional Formula(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(2.5)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃

119 g (0.5 mol) of 3-mercaptopropyltriethoxysilane was put into a2-liter separable flask equipped with a nitrogen-introducing duct, athermometer, a Dimroth condenser and a dropping funnel, and withstirring, 151.2 g (0.45 mol) of an ethanol solution of sodium ethoxidehaving an effective ingredient concentration of 20% was added thereto.Subsequently, this was heated up to 80° C. and stirred for 3 hours.Afterwards, this was cooled and transferred into a dropping funnel.

Next, 69.75 g (0.45 mol) of 1,6-dichlorohexane was put into a separableflask similar to the above, heated up to 80° C., and the reactionproduct of 3-mercaptopropyltriethoxysilane and sodium ethoxide wasslowly and dropwise added thereto. After the addition, this was stirredfor 5 hours at 80° C. Subsequently, this was cooled, and salt wasseparated from the obtained solution through filtration, and ethanol andexcessive 1,6-dichlorohexane were removed therefrom throughreduced-pressure distillation. The solution obtained was distilled underreduced pressure to obtain 137.7 g of a colorless transparent liquidwith a boiling point of 148 to 150° C./0.005 tort As a result of IRanalysis, ¹H-NMR analysis and mass spectrometry analysis (MS analysis),the product was a compound represented by(CH₃CH₂O)₃Si—(CH₂)₃S—(CH₂)₆—Cl. Through gas chromatography analysis (GCanalysis), the purity of the compound was 97.5%.

Next, 80 g of ethanol, 5.46 g (0.07 mol) of anhydrous sodium sulfide and3.36 g (0.105 mol) of sulfur were put into the same 0.5-liter separableflask as above, and heated up to 80° C. With stirring the solution,49.91 g (0.14 mol) of the above (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—Cl wasgradually and dropwise added thereto. After the addition, this wasstirred for 10 hours at 80° C. After the stirring, this was cooled, theformed salt was taken out through filtration, and then the solventethanol was evaporated away under reduced pressure. The obtained,red-brown transparent solution was analyzed through IR analysis, ¹H-NMRanalysis and ultra-critical chromatography analysis, which confirmedthat the product is a compound represented by an average compositionalformula,(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(2.5)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃. InGPC analysis, the purity of the product was 85.2%.

Examples 1 to 205 and Comparative Examples 1 to 16

According to the compounding recipes and kneading methods shown inTables 1 to 8, rubber components, silica, and silane coupling agentswere kneaded in the first stage (X) of kneading. In each stage of thekneading, a Banbury mixer was used for kneading.

In Tables 1 to 3, the maximum temperature of the rubber compositions wasadjusted to the temperature shown in the Tables. Further, among therubber compositions in Tables 4 to 8, when the temperature of the rubbercomposition when the chemical agents were added during the first stage(X) was 145 or 150° C., the maximum temperature of the rubbercomposition in the first stage (X) of kneading was adjusted to 155° C.in order to secure time for kneading the chemical agents which would beadded later. However, in all other cases, the maximum temperature of therubber composition in the first stage (X) of kneading was adjusted to150° C.

In Examples and Comparative Examples in Table 4, the maximum temperatureof every rubber composition in the stage (Y) of kneading was adjusted sothat it became 150° C.

Additionally, in Comparative Example 16, kneading was carried out in thesecond stage of kneading without addition of the chemical agents.

The low heat-generating properties (tan δ indices) of the 221 rubbercompositions obtained were evaluated according to the method mentionedabove. The results are shown in Tables 1 to 8.

TABLE 1 Example Mass parts 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Com-First Emulsion- 100 100 100 100 100 100 100 100 100 100 100 100 100 100100 pound stage of polymerized ing knead- SBR-1 *1 ingre- ing Carbonblack-1 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 dients N220 *2Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 Silane coupling 44 4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 3030 30 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 1,3-Diphenyl- 1 1 1 11 1 1 — — — — — — — — guanidine *6 2-Mercap- 0.6 — —— — — — — 0.6 0.60.6 0.6 0.6 — — — tobenzo- thiazole *7 Di-2- — 1 — — — — — — — — — — 1 11 benzothiazolyl disulfide *8 N-cyclohexyl-2- — — 1 — — — — 1 — — — — 1— — benzothiazolyl- sulfenamide *9 Tetrakis(2-ethyl- — — — 1 — — — — 1 —— — — 1 — hexyl)thiuram disulfide *10 N,N′- — — — — 1 — — — — 1 — — — —1 diethyl- thiourea *11 Zinc di- — — — — — 1 — — — — 1 — — — —benzyldithio- carbamate *12 Zinc isopropyl — — — — — — 1 — — — — 1 — — —xanthate *13 Last Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 stage ofTMDQ *14 knead- Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 2.5 ing 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 11 1 1 1 accelerator MBTS *8 Vulcanization 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 accelerator TBBS *15 Sulfur 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 rubbercomposition in first stage of kneading (° C.) Property of vulcanizedmaterial: 132 125 126 131 123 134 134 128 134 124 135 134 122 130 120tan δ index Example Mass parts 16 17 18 19 20 21 22 23 24 25 26 27 Com-First Emulsion- 100 100 100 100 100 100 100 100 100 100 100 100 poundstage of polymerized ing knead- SBR-1 *1 ingre- ing Carbon black-1 10 1010 10 10 10 10 10 10 10 10 10 dients N220 *2 Silica *3 50 50 50 50 50 5050 50 50 50 50 50 Silane coupling 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4Aromatic oil 30 30 30 30 30 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 22 2 2 2 2 2 2 Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 1,3-Diphenyl-— — — — — — — — — — — — guanidine *6 2-Mercap- — — — — — — — — — — — —tobenzo- thiazole *7 Di-2- 1 1 — — — — — — — — — — benzothiazolyldisulfide *8 N-cyclohexyl-2- — — 1 1 1 1 — — — — — — benzothiazolyl-sulfenamide *9 Tetrakis(2-ethyl- — — 1 — — — 1 1 1 — — — hexyl)thiuramdisulfide *10 N,N′- — — — 1 — — 1 — — 1 1 diethyl- thiourea *11 Zinc di-1 — — — 1 — — 1 — 1 — 1 benzyldithio- carbamate *12 Zinc isopropyl — 1 —— — 1 — — 1 — 1 1 xanthate *13 Last Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1stage of TMDQ *14 knead- Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 ing 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 acceleratorMBTS *8 Vulcanization 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 Maximum temperature of 150 150 150 150 150 150 150 150 150 150 150150 rubber composition in first stage of kneading (° C.) Property ofvulcanized material: 129 128 128 120 129 127 126 136 133 122 121 138 tanδ index

TABLE 2 Comparative Example Mass parts 1 2 3 4 5 6 7 8 9 CompoundingFirst Emulsion-polymerized SBR-1 *1 100 100 100 100 100 100 100 100 100ingredients stage of Carbon black-1 N220 *2 10 10 10 10 10 10 10 10 10kneading Silica *3 50 50 50 50 50 50 50 50 50 Silane coupling agent Si75*4 4 4 4 4 4 4 4 4 4 Aromatic oil 30 30 30 30 30 30 30 30 30 Stearicacid 2 2 2 2 2 2 2 2 2 Antioxidant 6PPD *5 1 1 1 1 1 1 1 1 11,3-Diphenylguanidine *6 —- 1 — — — — — — — 2-Mercaptobenzothiazole *7 —— 0.6 — — — — — — Di-2-benzothiazolyl disulfide *8 — — — 1 — — — — —N-cyclohexyl-2-benzothiazolyl- — — — — 1 — — — — sulfenamide *9Tetrakis(2-ethylhexyl)thiuram — — — — — 1 — — — disulfide *10N,N′-diethylthiourea *11 — — — — — — 1 — — Zinc dibenzyldithiocarbamate*12 — — — — — — — 1 — Zinc isopropyl xanthate *13 — — — — — — — — 1 LastAntioxidant TMDQ *14 1 1 1 1 1 1 1 1 1 stage of Zinc flower 2.5 2.5 2.52.5 2.5 2.5 2.5 2.5 2.5 kneading 1,3-Diphenylguanidine *6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 Vulcanization accelerator MBTS *8 1 1 1 1 1 1 11 1 Vulcanization accelerator TBBS *15 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature ofrubber composition 150 150 150 150 150 150 150 150 150 in first stage ofkneading (° C.) Property of vulcanized material: tan δ index 100 112 105101 107 105 102 105 103

TABLE 3 Example Mass parts 1 28 29 30 31 4 32 33 34 6 35 36 37 38 Com-First Emulsion-polymerized 100 100 100 100 100 100 100 100 100 100 100100 100 100 pounding stage of SBR-1 *1 ingre- knead- Carbon black-1 N220*2 10 10 10 10 10 10 10 10 10 10 10 10 10 10 dients ing Silica *3 50 5050 50 50 50 50 50 50 50 50 50 50 50 Silane coupling agent 4 4 4 4 4 4 44 4 4 4 4 4 4 Si75 *4 Aromatic oil 30 30 30 30 30 30 30 30 30 30 30 3030 30 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Antioxidant 6PPD *5 1 1 11 1 1 1 1 1 1 1 1 1 1 1,3-Diphenyl- 1 1 1 1 1 1 1 1 1 1 1 1 1 1guanidine *6 2-Mercaptobenzo- 0.6 0.6 0.6 0.6 0.6 — — — — — — — — —thiazole *7 Tetrakis(2-ethylhex- — — — — — 1 1 1 1 — — — — — yl)thiuramdisulfide *10 Zinc dibenzyldithiocarba- — — — — — — — — — 1 1 1 1 1 mate*12 Zinc isopropyl — — — — — — — — — — — — — — xanthate *13 LastAntioxidant TMDQ *14 1 1 1 1 1 1 1 1 1 1 1 1 1 1 stage of Zinc flower2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 knead-1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6ing guanidine *6 Vulcanization acceler- 1 1 1 1 1 1 1 1 1 1 1 1 1 1 atorMBTS *8 Vulcanization acceler- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 ator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 Maximum temperature of rubber composition 150 115125 140 170 150 125 140 170 150 115 125 140 170 in first stage ofkneading (° C.) Property of vulcanized material: tan δ index 132 118 125129 141 131 120 127 140 134 115 121 128 135 Example Mass parts 9 39 4041 11 42 43 44 12 45 46 47 Com- First Emulsion-polymerized 100 100 100100 100 100 100 100 100 100 100 100 pounding stage of SBR-1 *1 ingre-knead- Carbon black-1 N220 *2 10 10 10 10 10 10 10 10 10 10 10 10 dientsing Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 Silane coupling 4 4 44 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 30 30 30 3030 30 30 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 Antioxidant 6PPD *5 1 1 11 1 1 1 1 1 1 1 1 1,3-Diphenyl- — — — — — — — — — — — — guanidine *62-Mercaptobenzo- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6thiazole *7 Tetrakis(2-ethylhex- 1 1 1 1 — — — — — — — — yl)thiuramdisulfide *10 Zinc dibenzyldithiocarba- — — — — 1 1 1 1 — — — — mate *12Zinc isopropyl — — — — — — — — 1 1 1 1 xanthate *13 Last AntioxidantTMDQ *14 1 1 1 1 1 1 1 1 1 1 1 1 stage of Zinc flower 2.5 2.5 2.5 2.52.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 knead- 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 ing guanidine *6 Vulcanization acceler- 1 11 1 1 1 1 1 1 1 1 1 ator MBTS *8 Vulcanization acceler- 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of rubber composition150 125 140 170 150 125 140 170 150 125 140 170 in first stage ofkneading (° C.) Property of vulcanized material: tan δ index 134 129 132135 135 130 133 136 134 130 133 134

TABLE 4 Example Mass parts 23 48 49 50 51 24 52 53 54 27 55 Com- FirstEmulsion-polymerized 100 100 100 100 100 100 100 100 100 100 100pounding stage of SBR-1 *1 ingre- knead- Carbon black-1 N220 *2 10 10 1010 10 10 10 10 10 10 10 dients ing Silica *3 50 50 50 50 50 50 50 50 5050 50 Silane coupling 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil30 30 30 30 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 2 2 2 2 2Antioxidant 6PPD *5 1 1 1 1 1 1 1 1 1 1 1 1,3-Diphenyl- — — — — — — — —— — — guanidine *6 2-Mercaptobenzo- — — — — — — — — — — — thiazole *7Tetrakis(2-ethylhex- 1 1 1 1 1 1 1 1 1 — — yl)thiuram disulfide *10 Zincdibenzyldithiocarba- 1 1 1 1 1 — — — — 1 1 mate *12 Zinc isopropyl — — —— — 1 1 1 1 1 1 xanthate *13 Last Antioxidant TMDQ * 14 1 1 1 1 1 1 1 11 1 1 stage of Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5knead- 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ingguanidine *6 Vulcanization acceler- 1 1 1 1 1 1 1 1 1 1 1 ator MBTS *8Vulcanization acceler- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 atorTBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximumtemperature of rubber composition 150 115 125 140 170 150 125 140 170150 115 in first stage of kneading (° C.) Property of vulcanizedmaterial: tan δ index 136 118 124 132 144 133 122 129 138 138 119Example Comparative Example Mass parts 56 57 58 1 2 3 6 8 9 Com- FirstEmulsion-polymerized 100 100 100 100 100 100 100 100 100 pounding stageof SBR-1 *1 ingre- knead- Carbon black-1 N220 *2 10 10 10 10 10 10 10 1010 dients ing Silica *3 50 50 50 50 50 50 50 50 50 Silane coupling 4 4 44 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 30 30 30 30Stearic acid 2 2 2 2 2 2 2 2 2 Antioxidant 6PPD *5 1 1 1 1 1 1 1 1 11,3-Diphenyl- — — — — 1 — — — — guanidine *6 2-Mercaptobenzo- — — — — —0.6 — — — thiazole *7 Tetrakis(2-ethylhex- — — — — — — 1 — — yl)thiuramdisulfide *10 Zinc dibenzyldithiocarba- 1 1 1 — — — — 1 — mate *12 Zincisopropyl 1 1 1 — — — — — 1 xanthate *13 Last Antioxidant TMDQ * 14 1 11 1 1 1 1 1 1 stage of Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5knead- 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ing guanidine*6 Vulcanization acceler- 1 1 1 1 1 1 1 1 1 ator MBTS *8 Vulcanizationacceler- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ator TBBS *15 Sulfur 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of rubbercomposition 125 140 170 150 150 150 150 150 150 in first stage ofkneading (° C.) Property of vulcanized material: tan δ index 128 133 145100 112 105 105 105 103

TABLE 5 Example Mass parts 59 60 61 62 63 64 65 66 67 68 69 Com- FirstEmulsion- 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.7568.75 pound- stage of polymerized ing knead- SBR-2 *16 ingre- ingSolution- 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.7568.75 dients polymerized SBR-1 *17 Carbon black-1 10 10 10 10 10 10 1010 10 10 10 N220 *2 Silica *3 80 80 80 80 80 80 80 80 80 80 80 Silanecoupling 6.5 — — — 6.5 — — — 6.5 — — agent Si75 *4 Silane coupling — 6.5— — — 6.5 — — — 6.5 — agent NXT *18 Silane coupling — — 6.5 — — — 6.5 —— — 6.5 agent NXT-Z *19 Silane coupling — — — 6.5 — — — 6.5 — — — agent*20 Aromatic oil 5 5 5 5 5 5 5 5 5 5 5 Stearic acid 2 2 2 2 2 2 2 2 2 22 Antioxidant 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 1,3-Diphenyl- 1 1 1 1 1 1 11 1 1 1 guanidine *6 2- 0.7 0.7 0.7 0.7 — — — — — — — Mercaptobenzo-thiazole *7 Tetrakis(2-ethyl- — — — — 1 1 1 1 — — — hexyl)thiuramdisulfide *10 Zinc — — — — — — — — 1 1 1 dibenzyldithio- carbamate *12Zinc isopropyl — — — — — — — — — — — xanthate *13 Last Zinc flower 3 3 33 3 3 3 3 3 3 3 stage of 1,3-Diphenyl- 1 1 1 1 1 1 1 1 1 1 1 knead-guanidine *6 ing Vulcanization 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.80.8 accelerator MBTS *8 Vulcanization 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Maximum temperature of 150 150 150 150 150 150 150 150 150150 150 rubber composition in first stage of kneading (° C.) Property ofvulcanized material: 128 133 134 140 130 138 136 145 133 139 142 tan δindex Example Mass parts 70 71 72 73 74 75 76 77 78 Com- First Emulsion-68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 pound- stage ofpolymerized ing knead- SBR-2 *16 ingre- ing Solution- 68.75 68.75 68.7568.75 68.75 68.75 68.75 68.75 68.75 dients polymerized SBR-1 *17 Carbonblack-1 10 10 10 10 10 10 10 10 10 N220 *2 Silica *3 80 80 80 80 80 8080 80 80 Silane coupling — 6.5 — — — 6.5 — — — agent Si75 *4 Silanecoupling — — 6.5 — — — 6.5 — — agent NXT *18 Silane coupling — — — 6.5 —— — 6.5 — agent NXT-Z *19 Silane coupling 6.5 — — — 6.5 — — — 6.5 agent*20 Aromatic oil 5 5 5 5 5 5 5 5 5 Stearic acid 2 2 2 2 2 2 2 2 2Antioxidant 1 1 1 1 1 1 1 1 1 6PPD *5 1,3-Diphenyl- 1 1 1 1 1 — — — —guanidine *6 2- — — — — — 0.7 0.7 0.7 0.7 Mercaptobenzo- thiazole *7Tetrakis(2-ethyl- — — — — — 0.8 0.8 0.8 0.8 hexyl)thiuram disulfide *10Zinc 1 — — — — — — — — dibenzyldithio- carbamate *12 Zinc isopropyl — 11 1 1 — — — — xanthate *13 Last Zinc flower 3 3 3 3 3 3 3 3 3 stage of1,3-Diphenyl- 1 1 1 1 1 1 1 1 1 knead- guanidine *6 ing Vulcanization0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 accelerator MBTS *8 Vulcanization1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 accelerator TBBS *15 Sulfur 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of 150 150 150 150 150150 150 150 150 rubber composition in first stage of kneading (° C.)Property of vulcanized material: 142 126 133 128 132 129 138 139 144 tanδ index

TABLE 6 Example Mass parts 79 80 81 82 83 84 85 86 87 88 89 Com- FirstEmulsion- 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.7568.75 pound- stage of polymerized ing knead- SBR-2 *16 ingre- Solution-68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 dientsing polymerized SBR-1 *17 Carbon black-1 10 10 10 10 10 10 10 10 10 1010 N220 *2 Silica *3 80 80 80 80 80 80 80 80 80 80 80 Silane coupling6.5 — — — 6.5 — — — 6.5 — — agent Si75 *4 Silane coupling — 6.5 — — —6.5 — — — 6.5 — agent NXT *18 Silane coupling — — 6.5 — — — 6.5 — — —6.5 agent NXT-Z *19 Silane coupling — — — 6.5 — — — 6.5 — — — agent *20Aromatic oil 5 5 5 5 5 5 5 5 5 5 5 Stearic acid 2 2 2 2 2 2 2 2 2 2 2Antioxidant 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 1,3-Diphenyl- — — — — — — — —— — — guanidine *6 2- 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 — — —Mercaptobenzo- thiazole *7 Tetrakis(2-ethyl- — — — — — — — — 1 1 1hexyl)thiuram disulfide *10 Zinc 0.7 0.7 0.7 0.7 — — — — 0.8 0.8 0.8dibenzyldithio- carbamate *12 Zinc isopropyl — — — — 0.5 0.5 0.5 0.5 — —— xanthate *13 Last Zinc flower 3 3 3 3 3 3 3 3 3 3 3 stage of1,3-Diphenyl- 1 1 1 1 1 1 1 1 1 1 1 knead- guanidine *6 ingVulcanization 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 acceleratorMBTS *8 Vulcanization 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5Maximum temperature of 150 150 150 150 150 150 150 150 150 150 150rubber composition in first stage of kneading (° C.) Property ofvulcanized material: 130 135 132 140 125 133 130 135 125 132 133 tan δindex Example Comparative Example Mass parts 90 91 92 93 94 10 11 12 13Com- First Emulsion- 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.7568.75 pound- stage of polymerized ing knead- SBR-2 *16 ingre- ingSolution- 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 68.75 dientspolymerized SBR-1 *17 Carbon black-1 10 10 10 10 10 10 10 10 10 N220 *2Silica *3 80 80 80 80 80 80 80 80 80 Silane coupling — 6.5 — — — 6.5 — —— agent Si75 *4 Silane coupling — — 6.5 — — — 6.5 — — agent NXT *18Silane coupling — — — 6.5 — — — 6.5 — agent NXT-Z *19 Silane coupling6.5 — — — 6.5 — — — 6.5 agent *20 Aromatic oil 5 5 5 5 5 5 5 5 5 Stearicacid 2 2 2 2 2 2 2 2 2 Antioxidant 1 1 1 1 1 1 1 1 1 6PPD *51,3-Diphenyl- — — — — — — — — — guanidine *6 2- — — — — — — — — —Mercaptobenzo- thiazole *7 Tetrakis(2-ethyl- 1 — — — — — — — —hexyl)thiuram disulfide *10 Zinc 0.8 0.8 0.8 0.8 0.8 — — — —dibenzyldithio- carbamate *12 Zinc isopropyl — 0.5 0.5 0.5 0.5 — — — —xanthate *13 Last Zinc flower 3 3 3 3 3 3 3 3 3 stage of 1,3-Diphenyl- 11 1 1 1 1 1 1 1 knead- guanidine *6 ing Vulcanization 0.8 0.8 0.8 0.80.8 0.8 0.8 0.8 0.8 accelerator MBTS *8 Vulcanization 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Maximum temperature of 150 150 150 150 150 150 150 150 150rubber composition in first stage of kneading (° C.) Property ofvulcanized material: 139 123 130 126 137 100 110 108 108 tan δ index

TABLE 7 Example Mass parts 95 96 97 98 99 100 101 102 103 104 105 106107 108 109 Com- First Emulsion- 100 100 100 100 100 100 100 100 100 100100 100 100 100 100 pound- stage of polymerized ing knead- SBR-1 *1ingre- ing Carbon black-1 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10dients N220 *2 Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50Silane coupling 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 22 2 2 2 2 2 2 2 Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 Second1,3-Diphenyl- 1 1 1 1 1 1 1 — — — — — — — — stage of guanidine *6 knead-2- 0.6 — — — — — — 0.6 0.6 0.6 0.6 0.6 — — — ing Mercaptobenzo- thiazole*7 Di-2- — 1 — — — — — — — — — — 1 1 1 benzothiazolyl disulfide *8N-cyclohexyl-2- — — 1 — — — — 1 — — — — 1 — — benzothiazolyl-sulfenamide *9 Tetrakis(2-ethyl- — — — 1 — — — — 1 — — — — 1 —hexyl)thiuram disulfide *10 N,N′-diethyl- — — — — 1 — — — — 1 — — — — 1thiourea *11 Zinc — — — — — 1 — — — — 1 — — — — dibenzyldithio-carbamate *12 Zinc isopropyl — — — — — — 1 — — — — 1 — — — xanthate *13Last Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 stage of TMDQ *14 knead-Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5ing 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1accelerator MBTS *8 Vulcanization 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of 150 150150 150 150 150 150 150 150 150 150 150 150 150 150 rubber compositionin second stage of kneading (° C.) Property of vulcanized material: 135128 127 135 126 140 136 129 140 128 143 140 124 131 120 tan δ indexCompar- Example ative Mass parts 110 111 112 113 114 115 116 117 118 119120 121 Example 1 Com- First Emulsion- 100 100 100 100 100 100 100 100100 100 100 100 100 pound- stage of polymerized ing knead- SBR-1 *1ingre- ing Carbon black-1 10 10 10 10 10 10 10 10 10 10 10 10 10 dientsN220 *2 Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50 Silane coupling4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 3030 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 Antioxidant1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 Second 1,3-Diphenyl- — — — — — — — — —— — — — stage of guanidine *6 knead- 2- — — — — — — — — — — — — — ingMercaptobenzo- thiazole *7 Di-2- 1 1 — — — — — — — — — — —benzothiazolyl disulfide *8 N-cyclohexyl-2- — — 1 1 1 1 — — — — — — —benzothiazolyl- sulfenamide *9 Tetrakis(2-ethyl- — — 1 — — — 1 1 1 — — —— hexyl)thiuram disulfide *10 N,N′-diethyl- — — — 1 — — 1 — — 1 1 — —thiourea *11 Zinc 1 — — — 1 — — 1 — 1 — 1 — dibenzyldithio- carbamate*12 Zinc isopropyl — 1 — — — 1 — — 1 — 1 1 — xanthate *13 LastAntioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 stage of TMDQ *14 knead- Zincflower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 ing1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 1 accelerator MBTS *8Vulcanization 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 Maximum temperature of 150 150 150 150 150 150 150 150 150 150150 150 — rubber composition in second stage of kneading (° C.) Propertyof vulcanized material: 135 134 129 121 134 127 135 144 136 123 124 148100 tan δ index

TABLE 8 Example Mass parts 122 123 124 125 126 127 128 129 130 131 132133 134 135 136 Com- First Emulsion- 100 100 100 100 100 100 100 100 100100 100 100 100 100 100 pound- stage of polymerized ing knead- SBR-1 *1ingre- ing Carbon black-1 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10dients N220 *2 Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50Silane coupling 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 22 2 2 2 2 2 2 2 Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5Delayed 1,3-Diphenyl- 1 1 1 1 1 1 1 — — — — — — — — addition guanidine*6 during 2- 0.6 — — — — — — 0.6 0.6 0.6 0.6 0.6 — — — firstMercaptobenzo- stage of thiazole *7 knead- Di-2- — 1 — — — — — — — — — —1 1 1 ing benzothiazolyl disulfide *8 N-cyclohexyl-2- — — 1 — — — — 1 —— — — 1 — — benzothiazolyl- sulfenamide *9 Tetrakis(2-ethyl- — — — 1 — —— — 1 — — — — 1 — hexyl)thiuram disulfide *10 N,N′-diethyl- — — — — 1 —— — — 1 — — — — 1 thiourea *11 Zinc — — — — — 1 — — — — 1 — — — —dibenzyldithio- carbamate *12 Zinc isopropyl — — — — — — 1 — — — — 1 — —— xanthate *13 Last Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 stage ofTMDQ *14 knead- Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 9.5 2.5 9.52.5 2.5 2.5 2.5 ing 1,3-Diphenyl- 06 06 06 06 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 11 1 accelerator MBTS *8 Vulcanization 06 06 06 06 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Time elapsed from addition 90 9090 90 90 90 90 90 90 90 90 90 90 90 90 of silica and silane couplingagent to delayed addition of accelerator (sec) Temperature of rubbercomposition 130 130 130 130 130 130 130 130 130 130 130 130 130 130 130when delayed addiition of accelerator was made (° C.) Maximumtemperature of 150 150 150 150 150 150 150 150 150 150 150 150 150 150150 rubber composition in first stage of kneading (° C.) Property ofvulcanized material: 138 126 125 137 124 138 138 133 139 126 140 143 123134 121 tan δ index Compar- Example ative Mass parts 137 138 139 140 141142 143 144 145 146 147 148 Example 1 Com- First Emulsion- 100 100 100100 100 100 100 100 100 100 100 100 100 pound- stage of polymerized ingknead- SBR-1 *1 ingre- ing Carbon black-1 10 10 10 10 10 10 10 10 10 1010 10 10 dients N220 *2 Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50Silane coupling 4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil 3030 30 30 30 30 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 22 Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 Delayed 1,3-Diphenyl- —— — — — — — — — — — — — addition guanidine *6 during 2- — — — — — — — —— — — — — first Mercaptobenzo- stage of thiazole *7 knead- Di-2- 1 1 — —— — — — — — — — — ing benzothiazolyl disulfide *8 N-cyclohexyl-2- — — 11 1 1 — — — — — — — benzothiazolyl- sulfenamide *9 Tetrakis(2-ethyl- — —1 — — — 1 1 1 — — — — hexyl)thiuram disulfide *10 N,N′-diethyl- — — — 1— — 1 — — 1 1 — — thiourea *11 Zinc 1 — — — 1 — — 1 — 1 — 1 —dibenzyldithio- carbamate *12 Zinc isopropyl — 1 — — — 1 — — 1 — 1 1 —xanthate *13 Last Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 stage of TMDQ*14 knead- Zinc flower 2.5 2.5 2.5 2.5 2.5 9.5 2.5 9.5 2.5 2.5 2.5 2.52.5 ing 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 1 acceleratorMBTS *8 Vulcanization 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Time elapsed from addition 90 90 90 90 90 90 90 90 90 90 9090 — of silica and silane coupling agent to delayed addition ofaccelerator (sec) Temperature of rubber composition 130 130 130 130 130130 130 130 130 130 130 130 — when delayed addiition of accelerator wasmade (° C.) Maximum temperature of 150 150 150 150 150 150 150 150 150150 150 150 150 rubber composition in first stage of kneading (° C.)Property of vulcanized material: 128 135 128 120 134 125 137 148 139 120122 150 100 tan δ index

TABLE 9 Example Mass parts 122 149 150 151 152 153 154 155 132 Com-First Emulsion-polymerized 100 100 100 100 100 100 100 100 100 pound-stage of SBR-1 *1 ing knead- Carbon black-1 N220 *2 10 10 10 10 10 10 1010 10 ingre- ing Silica *3 50 50 50 50 50 50 50 50 50 dients Silanecoupling 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 3030 30 30 Stearic acid 2 2 2 2 2 2 2 2 2 Antioxidant 6PPD *5 1 1 1 1 1 11 1 1 Delayed 1,3-Diphenyl- 1 1 1 1 1 1 1 1 — addition guanidine *6during 2-Mercaptobenzo- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 firstthiazole *7 stage of Di-2-benzothiazolyl — — — — — — — — — knead-disulfide *8 ing N-cyclohexyl-2-benzo- — — — — — — — — —thiazolyl-sulfenamide *9 Tetrakis(2-ethylhex- — — — — — — — — — yl)thiuram disulfide *10 N,N′-diethylthiourea *11 — — — — — — — — — Zincdibenzyldithiocarba- — — — — — — — — 1 mate *12 Zinc isopropyl — — — — —— — — — xanthate *13 Last Antioxidant TMDQ * 14 1 1 1 1 1 1 1 1 1 stageof Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 knead- 1,3-Diphenyl-0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ing guanidine *6 Vulcanizationacceler- 1 1 1 1 1 1 1 1 1 ator MBTS *8 Vulcanization acceler- 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 ator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Time elapsed from addition of silica and silane 90 15 30 60120 150 180 210 90 coupling agent to delayed addition of accelerator(sec) Temperature of rubber composition when 130 80 100 120 135 140 145150 130 delayed addition of accelerator was made (° C.) Maximumtemperature of rubber composition 150 150 150 150 150 150 155 155 150 infirst stage of kneading (° C.) Property of vulcanized material: tan δindex 138 130 134 137 138 137 136 135 140 Compar- Example ative Massparts 156 157 158 159 160 161 162 Example 1 Com- FirstEmulsion-polymerized 100 100 100 100 100 100 100 100 pound- stage ofSBR-1 *1 ing knead- Carbon black-1 N220 *2 10 10 10 10 10 10 10 10ingre- ing Silica *3 50 50 50 50 50 50 50 50 dients Silane coupling 4 44 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 30 30 30 Stearicacid 2 2 2 2 2 2 2 2 Antioxidant 1 1 1 1 1 1 1 1 6PPD *5 Delayed1,3-Diphenyl- — — — — — — — — addition guanidine *6 during2-Mercaptobenzo- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 — first thiazole *7 stageof Di-2-benzothiazolyl — — — — — — — — knead- disulfide *8 ingN-cyclohexyl-2-benzo- — — — — — — — — thiazolyl-sulfenamide *9Tetrakis(2-ethylhex- — — — — — — — — yl) thiuram disulfide *10N,N′-diethylthiourea *11 — — — — — — — — Zinc dibenzyldithiocarba- 1 1 11 1 1 1 — mate *12 Zinc isopropyl — — — — — — — — xanthate *13 LastAntioxidant TMDQ * 14 1 1 1 1 1 1 1 1 stage of Zinc flower 2.5 2.5 2.52.5 2.5 2.5 2.5 2.5 knead- 1,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6ing guanidine *6 Vulcanization acceler- 1 1 1 1 1 1 1 1 ator MBTS *8Vulcanization acceler- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ator TBBS *15Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Time elapsed from addition ofsilica and silane 15 30 60 120 150 180 210 — coupling agent to delayedaddition of accelerator (sec) Temperature of rubber composition when 80100 120 135 140 145 150 — delayed addition of accelerator was made (°C.) Maximum temperature of rubber composition 150 150 150 150 150 155155 150 in first stage of kneading (° C.) Property of vulcanizedmaterial: tan δ index 134 137 140 140 139 137 137 100

TABLE 10 Example Mass parts 163 164 165 166 167 168 169 170 171 172 173174 175 176 177 Com- First Solution- 100 100 100 100 100 100 100 100 100100 100 100 100 100 100 pound- stage of polymerized ing knead- SBR-2 *21ingre- ing Carbon black-1 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10dients N220 *2 Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50Silane coupling 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 Stearic acid — — —— — — — —— — — — —— — — — Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *51,3-Diphenyl- 1 1 1 1 1 1 1 — — — — — — — — guanidine *6 2- 0.6 — — — —— — 0.6 0.6 0.6 0.6 0.6 — — — Mercaptobenzo- thiazole *7 Di-2- — 1 — — —— — — — — — — 1 1 1 benzothiazolyl disulfide *8 N-cyclohexyl-2- — — 1 —— — — 1 — — — — 1 — — benzothiazolyl- sulfenamide *9 Tetrakis(2-ethyl- —— — 1 — — — — 1 — — — — 1 — hexyl)thiuram disulfide *10 N,N′-diethyl- —— — — 1 — — — — 1 — — — — 1 thiourea *11 Zinc — — — — — 1 — — — — 1 — —— — dibenzyldithio- carbamate *12 Zinc isopropyl — — — — — —— 1 — — — —1 — — — xanthate *13 Last Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2stage of Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 knead- TMDQ *14 ingZinc flower 2.5 2.5 2.5 1.5 2.5 2.5 1.5 2.5 2.5 1.5 2.5 1.5 2.5 2.5 1.51,3-Diphenyl- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 guanidine *6 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 acceleratorMBTS *8 Vulcanization 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 accelerator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of 150 150 150 150 150150 150 150 150 150 150 150 150 150 150 rubber composition in firststage of kneading (° C.) Property of vulcanized material: 140 134 130133 125 138 139 130 141 130 142 136 125 132 124 tan δ index Compar-ative Example Example Mass parts 178 179 180 181 182 183 184 185 186 187188 189 14 15 Com- First Solution- 100 100 100 100 100 100 100 100 100100 100 100 100 100 pound- stage of polymerized ing knead- SBR-2 *21ingre- ing Carbon black-1 10 10 10 10 10 10 10 10 10 10 10 10 10 10dients N220 *2 Silica *3 50 50 50 50 50 50 50 50 50 50 50 50 50 50Silane coupling 4 4 4 4 4 4 4 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil30 30 30 30 30 30 30 30 30 30 30 30 30 30 Stearic acid — — — — — — — — —— — — 2 — Antioxidant 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6PPD *5 1,3-Diphenyl-— — — — — — — — — — — — — — guanidine *6 2- — — — — — — — — — — — — — —Mercaptobenzo- thiazole *7 Di-2- 1 1 — — — — — — — — — — — —benzothiazolyl disulfide *8 N-cyclohexyl-2- — — 1 1 1 1 — — — — — — — —benzothiazolyl- sulfenamide *9 Tetrakis(2-ethyl- — — 1 — — — 1 1 1 — — —— — hexyl)thiuram disulfide *10 N,N′-diethyl- — — — 1 — — 1 — — 1 1 — —— thiourea *11 Zinc 1 — — — 1 — — 1 — 1 — 1 — — dibenzyldithio-carbamate *12 Zinc isopropyl — 1 — — — 1 — — 1 — 1 1 — — xanthate *13Last Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 — 2 stage of Antioxidant 1 1 11 1 1 1 1 1 1 1 1 1 1 knead- TMDQ *14 ing Zinc flower 2.5 1.5 2.5 2.51.5 2.5 1.5 2.5 2.5 1.5 2.5 2.5 2.5 2.5 1,3-Diphenyl- 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 guanidine *6 Vulcanization 1 1 11 1 1 1 1 1 1 1 1 1 1 accelerator MBTS *8 Vulcanization 0.6 0.6 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 accelerator TBBS *15 Sulfur 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperatureof 150 150 150 150 150 150 150 150 150 150 150 150 150 150 rubbercomposition in first stage of kneading (° C.) Property of vulcanizedmaterial: 130 130 131 124 132 130 135 142 143 124 125 145 100 115 tan δindex

TABLE 11 Example Mass parts 1 190 191 192 193 11 194 195 196 Com- FirstEmulsion-polymerized 100 100 100 100 100 100 100 100 100 pound- stage ofSBR-1 *1 ing knead- Carbon black-1 N220 *2 10 20 30 40 50 10 20 30 40ingre- ing Silica *3 50 40 30 20 10 50 40 30 20 dients Silane coupling 44 4 4 4 4 4 4 4 agent Si75 *4 Aromatic oil 30 30 30 30 30 30 30 30 30Stearic acid 2 2 2 2 2 2 2 2 2 Antioxidant 6PPD *5 1 1 1 1 1 1 1 1 11,3-Diphenyl- 1 1 1 1 1 — — — — guanidine *6 2-Mercaptobenzo- 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 thiazole *7 Di-2-benzothiazolyl — — — — — —— — — disulfide *8 N-cyclohexyl-2-benzo- — — — — — — — — —thiazolyl-sulfenamide *9 Tetrakis(2-ethylhex- — — — — — — — — —yl)thiuram disulfide *10 N,N′-diethylthiourea *11 — — — — — — — — — Zincdibenzyldithiocarba- — — — — — 1 1 1 1 mate *12 Zinc isopropyl — — — — —— — — — xanthate *13 Last Antioxidant TMDQ * 14 1 1 1 1 1 1 1 1 1 stageof Zinc flower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 knead- 1,3-Diphenyl-0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ing guanidine *6 Vulcanizationacceler- 1 1 1 1 1 1 1 1 1 ator MBTS *8 Vulcanization acceler- 0.6 0.60.6 0.6 0.6 0.6 0.6 0.6 0.6 ator TBBS *15 Sulfur 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Proportion of silica in filler (%) 83 67 50 33 17 83 67 5033 Maximum temperature of rubber composition 150 150 150 150 150 150 150150 150 in first stage of kneading (° C.) Property of vulcanizedmaterial: tan δ index 132 126 120 114 108 135 129 121 114 Compar-Example ative Mass parts 197 21 198 199 200 201 Example 1 Com- FirstEmulsion-polymerized 100 100 100 100 100 100 100 pound- stage of SBR-1*1 ing knead- Carbon black-1 N220 *2 50 10 20 30 40 50 10 ingre- ingSilica *3 10 50 40 30 20 10 50 dients Silane coupling 4 4 4 4 4 4 4agent Si75 *4 Aromatic oil 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 22 Antioxidant 6PPD *5 1 1 1 1 1 1 1 1,3-Diphenyl- — — — — — — —guanidine *6 2-Mercaptobenzo- 0.6 — — — — — — thiazole *7Di-2-benzothiazolyl — — — — — — — disulfide *8 N-cyclohexyl-2-benzo- — 11 1 1 1 — thiazolyl-sulfenamide *9 Tetrakis(2-ethylhex- — — — — — — —yl)thiuram disulfide *10 N,N′-diethylthiourea *11 — — — — — — — Zincdibenzyldithiocarba- 1 — — — — — — mate *12 Zinc isopropyl — 1 1 1 1 1 —xanthate *13 Last Antioxidant TMDQ * 14 1 1 1 1 1 1 1 stage of Zincflower 2.5 2.5 2.5 2.5 2.5 2.5 2.5 knead- 1,3-Diphenyl- 0.6 0.6 0.6 0.60.6 0.6 0.6 ing guanidine *6 Vulcanization acceler- 1 1 1 1 1 1 1 atorMBTS *8 Vulcanization acceler- 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ator TBBS *15Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Proportion of silica in filler (%) 1783 67 50 33 17 83 Maximum temperature of rubber composition 150 150 150150 150 150 150 in first stage of kneading (° C.) Property of vulcanizedmaterial: tan δ index 106 127 122 116 110 106 100

TABLE 12 Compar- ative Example Example Mass parts 95 202 203 204 205 116 Compounding First Emulsion-polymerized SBR-1 *1 100 100 100 100 100100 100 ingredients stage of Carbon black-1 N220 *2 10 10 10 10 10 10 10kneading Silica *3 50 50 50 50 50 50 50 Silane coupling agent Si75 *4 44 4 4 4 4 4 Aromatic oil 30 30 30 30 30 30 30 Stearic acid 2 2 2 2 2 2 2Antioxidant 6PPD *5 1 1 1 1 1 1 1 Second 1,3-Diphenylguanidine *6 1 1 11 1 — — stage of 2-Mercaptobenzothiazole *7 0.6 0.6 0.6 0.6 0.6 — —kneading Last Antioxidant TMDQ *14 1 1 1 1 1 1 1 stage of Zinc flower2.5 2.5 2.5 2.5 2.5 2.5 2.5 kneading 1,3-Diphenylguanidine *6 0.6 0.60.6 0.6 0.6 0.6 0.6 Vulcanization accelerator MBTS *8 1 1 1 1 1 1 1Vulcanization accelerator TBBS *15 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Sulfur1.5 1.5 1.5 1.5 1.5 1.5 1.5 Maximum temperature of rubber composition150 185 155 140 125 — 170 in second stage of kneading (° C.) Property ofvulcanized material: tan δ index 135 148 140 129 121 100 105

NOTES TO TABLES 1 TO 8

In Tables 1 to 8, the first stage (X) of kneading, the second stage (Y)of kneading, and the last stage (Z) of kneading are abbreviated as“first stage of kneading,” “second stage of kneading,” and “last stageof kneading,” respectively.

-   *1: JSR's emulsion-polymerized styrene-butadiene copolymer rubber    (SBR), trade name “#1500”-   *2: Trade name “#80” produced by Asahi Carbon Co., Ltd.-   *3: Tosoh Silica's trade name “Nipsil AQ”, BET specific surface area    220 m²/g-   *4: Bis(3-triethoxysilylpropyl)disulfide (mean sulfur chain length:    2.35), Evonik's silane coupling agent, trade name “Si75” (registered    trademark)-   *5: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, by Ouchi    Shinko Chemical, trade name “Nocrac 6C”-   *6: 1,3-Diphenylguanidine, Sanshin Chemical's trade name “Sanceler    D”-   *7: 2-Mercaptobenzothiazole; trade name “Nocceler M-P” produced by    Ouchi Shinko Chemical Co., Ltd.-   *8: Di-2-benzothiazolyl disulfide, Sanshin Chemical's trade name    “Sanceler DM”-   *9: N-Cyclohexyl-2-benzothiazolylsulfenamide; trade name “Nocceler    CZ” produced by Ouchi Shinko Chemical Industrial Co., Ltd.-   *10: Tetrakis(2-ethylhexyl)thiuram disulfide; trade name “Nocceler    TOT-N” produced by Ouchi Shinko Chemical Industrial Co., Ltd.-   *11: N,N′-diethylthiourea; trade name “Nocceler EUR” produced by    Ouchi Shinko Chemical Industrial Co., Ltd.-   *12: Zinc dibenzyldithiocarbamate; trade name “Nocceler ZTC”    produced by Ouchi Shinko Chemical Industrial Co., Ltd.-   *13: Zinc isopropyl xanthate; trade name “Nocceler ZIX-O” produced    by Ouchi Shinko Chemical Industrial Co., Ltd.-   *14: 2,2,4-Trimethyl-1,2-dihydroquinoline polymer; trade name    “Nocrac 224” produced by Ouchi Shinko Chemical Industrial Co., Ltd.-   *15: N-tert-butyl-2-benzothiazolylsulfenamide, Sanshin Chemical's    trade name “Sanceler NS”-   *16: JSR's emulsion-polymerized styrene-butadiene copolymer rubber    (SBR), trade name “#1712”-   *17: Asahi Kasei's solution-polymerized styrene-butadiene copolymer    rubber (SBR), trade name “Tufdene 3835”-   *18: 3-Octanoylthiopropyltriethoxysilane; trade name “NXT silane”    (registered trademark) produced by Momentive Performance Materials    Inc.-   *19: A silane coupling agent represented by the above chemical    formula (VII); trade name “NXT-Z” (registered trademark) produced by    Momentive Performance Materials Inc.-   *20: silane coupling agent obtained in Production Example 1 and    represented by the following average compositional formula:    (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(2.5)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃-   *21: Asahi Kasei's solution-polymerized styrene-butadiene copolymer    rubber (SBR), trade name “Tufdene 2000”

INDUSTRIAL APPLICABILITY

According to the production method for a rubber composition of thepresent invention, it is possible to obtain a rubber compositionexcellent in low-heat-generation property with successfully inhibitingthe coupling function activity of the silane coupling agent used fromlowering and with further increasing the coupling activity thereof, andis therefore favorably used as a production method for constitutivemembers of various types of pneumatic tires for passenger cars,small-size trucks, minivans, pickup trucks and big-size vehicles(trucks, buses, construction vehicles, etc.) and others, especially fortread members of pneumatic radial tires.

The invention claimed is:
 1. A process for producing a rubbercomposition comprising a rubber component (A) comprising at least oneselected from the group consisting of natural rubbers and syntheticdiene rubbers, a filler containing an inorganic filler (B), a silanecoupling agent (C), and at least two kinds of chemical agents (D) and(E) selected from the group consisting of guanidines, sulfenamides,thiazoles, thiurams, dithiocarbamates, thioureas, and xanthates, whereinthe rubber composition is kneaded in a kneading step comprising three ormore stages wherein, in the first stage (X) of kneading, the rubbercomponent (A), all or a portion of the inorganic filler (B), all or aportion of the silane coupling agent (C) are kneaded; in a stage (Y)after the first stage but before the last stage of kneading, at leasttwo kinds of the chemical agents (D) and (E) selected from the groupconsisting of guanidines, sulfenamides, thiazoles, thiurams,dithiocarbamates, thioureas, and xanthates are added and kneaded; and,in the last stage (Z) of kneading, a vulcanizing agent and a guanidineor thiazole are added and kneaded; wherein the maximum temperature ofthe rubber composition in the first stage (X) of kneading is 120 to 190°C., and the maximum temperature of the rubber composition in the stage(Y) of kneading is 130 to 175° C.
 2. The process for producing a rubbercomposition according to claim 1, wherein the silane coupling agent (C)is at least one compound selected from the group consisting of thecompounds represented by the following general formulae (I) to (IV):[Chemical Formula 1](R¹O)_(3−p)(R²)_(p)Si—R³—S_(a)—R³—Si(OR¹)_(3−r)(R²)_(r)  (I) in theformula, R¹'s may be the same or different and are each a linear,cyclic, or branched alkyl group, having 1 to 8 carbon atoms, or a linearor branched alkoxyalkyl group having 2 to 8 carbon atoms; R²'s may bethe same or different and are each a linear, cyclic, or branched alkylgroup, having 1 to 8 carbon atoms; R³'s may be the same or different andare each a linear or branched alkylene group, having 1 to 8 carbonatoms; a is 2 to 6 as an average value; and p and r may be the same ordifferent and are each 0 to 3 as an average value, provided that p and rare not 3 at the same time;

in the formula, R⁴ is a monovalent group selected from the groupconsisting of —Cl, —Br, R⁹O—, R⁹(C═O)O—, R⁹R¹⁰C═NO—, R⁹R¹⁰CNO—, R⁹R¹⁰N—,and —(OSiR⁹R¹⁰)_(h)(OSiR⁹R¹⁰R¹¹), wherein R⁹, R¹⁰, and R¹¹ may be thesame or different and are each a hydrogen atom or a monovalenthydrocarbon group having 1 to 18 carbon atoms, and h is 1 to 4 as anaverage value; R⁵ represents R⁴, a hydrogen atom, or a monovalenthydrocarbon group having 1 to 18 carbon atoms; R⁶ represents R⁴, R⁵, ahydrogen atom, or a —[O(R¹²O)_(j)]_(0.5)— group, wherein R¹² is analkylene group having 1 to 18 carbon atoms and j is an integer from 1 to4; R⁷ represents a divalent hydrocarbon group having 1 to 18 carbonatoms; R⁸ represents a monovalent hydrocarbon group having 1 to 18carbon atoms; and x, y, and z are numbers which satisfy therelationships: x+y+2z=3, 0≦x≦3, 0≦y≦2, and 0≦z≦1; [Chemical Formula 3](R¹³O)_(3−s)(R¹⁴)_(s)Si—R¹⁵—S_(k)—R¹⁶—S_(k)—R¹⁵—Si(OR¹³)_(3−t)(R¹⁴)_(t)  (III)in the formula, R¹³'s may be the same or different and are each alinear, cyclic, or branched alkyl group, having 1 to 8 carbon atoms, ora linear or branched alkoxyalkyl group having 2 to 8 carbon atoms; R¹⁴'smay be the same or different and are each a linear, cyclic, or branchedalkyl group, having 1 to 8 carbon atoms; R¹⁵'s may be the same ordifferent and are each a linear or branched alkylene group, having 1 to8 carbon atoms; R¹⁶ is a divalent group of any of general formulae—S—R¹⁷—S—, —R¹⁸—S_(m1)—R¹⁹—, and —R²⁰—S_(m2)—R²¹—S_(m3)—R²²—, whereinR¹⁷ to R²² may be the same or different and are each a divalenthydrocarbon group, a divalent aromatic group, or a divalent organicgroup containing a heteroatom other than sulfur or oxygen, each having 1to 20 carbon atoms; and m1, m2, and m3 may be the same or different andare each 1 or more but less than 4 as an average value; k's may be thesame or different and are each 1 to 6 as an average value; s and t maybe the same or different and are each 0 to 3 as an average value,provided that s and t are not 3 at the same time;

in the formula, R²³ is a linear, branched, or cyclic alkyl group, having1 to 20 carbon atoms; G's may be the same or different and are each analkanediyl group or an alkenediyl group, having 1 to 9 carbon atoms;Z^(a)'s may be the same or different and are each a group which can bondto two silicon atoms and is selected from [—O—]_(0.5), [—O-G-]_(0.5), or[—O-G-O—]_(0.5); Z^(b)'s may be the same or different and are each agroup which can bond to two silicon atoms and is a functional grouprepresented by [—O-G-O—]_(0.5); Z^(c)'s may be the same or different andare each a functional group represented by —Cl, —Br, —OR^(a),R^(a)C(═O)O—, R^(a)R^(b)C═NO—, R^(a)R^(b)N—, R^(a)—, HO-G-O—, wherein Gis the same as above; R^(a) and R^(b) may be the same or different andare each a linear, branched, or cyclic alkyl group, having 1 to 20carbon atoms; and m, n, u, v, and w may be the same or different and1≦m≦20, 0≦n≦20, 0≦u≦3, 0≦v≦2, 0≦w≦1, and (u/2)+v+2w=2 or 3; wherein an Aportion is represented by [R²³—C(═O)—S-G-SiZ^(a) _(u)Z^(b) _(v)Z^(c)_(w)]_(m) and a B portion is represented by [HS-G-SiZ^(a) _(u)Z^(b)_(v)Z^(c) _(w)]_(n); when the A portion exists in plurality, Z^(a)_(u)'s, Z^(b) _(v)'s, and Z^(c) _(w)'s in the plural A portions may eachbe the same or different; and, when the B portion exists in plurality,Z^(a) _(u)'s, Z^(b) _(v)'s, and Z^(c) _(w)'s in the plural B portionsmay each be the same or different.
 3. The method for producing a rubbercomposition according to claim 2, the silane coupling agent (C) is acompound represented by the general formula (I).
 4. The method forproducing a rubber composition according to claim 1, wherein theinorganic filler (B) is silica.
 5. The process for producing a rubbercomposition according to claim 1, wherein the filler further containscarbon black.
 6. The method for producing a rubber composition accordingto claim 1, wherein the inorganic filler (B) accounts for at least 40%by mass of the filler.
 7. The process for producing a rubber compositionaccording to claim 1, wherein, in stage (Y), one of the chemical agents(D) and (E) is selected from the group consisting of guanidines.
 8. Theprocess for producing a rubber composition according to claim 1,wherein, in stage (Y), one of the chemical agents (D) and (E) isselected from the group consisting of thiazoles.
 9. The process forproducing a rubber composition according to claim 1, wherein, in stage(Y), one of the chemical agents (D) and (E) is selected from the groupconsisting of sulfenamides.
 10. The process for producing a rubbercomposition according to claim 1, wherein, in stage (Y), one of thechemical agents (D) and (E) is selected from the group consisting ofthiurams.
 11. The process for producing a rubber composition accordingto claim 1, wherein, in stage (Y), one of the chemical agents (D) and(E) is selected from the group consisting of dithiocarbamates.
 12. Theprocess for producing a rubber composition according to claim 1,wherein, in stage (Y), one of the chemical agents (D) and (E) isselected from the group consisting of thioureas.
 13. The process forproducing a rubber composition according to claim 1, wherein, in stage(Y), one of the chemical agents (D) and (E) is selected from the groupconsisting of xanthates.
 14. The method for producing a rubbercomposition according to claim 1, wherein the guanidine in stages (Y)and (Z) is at least one compound selected from the group consisting of1,3-diphenylguanidine, 1,3-di-o-tolylguanidine and 1-o-tolylbiguanide.15. The process for producing a rubber composition according to claim 1,wherein, in stage (Y), the sulfonamides areN-cyclohexyl-2-benzothiazolylsulfenamide,N-tert-butyl-2-benzothiazolylsulfenamide and combinations thereof. 16.The process for producing a rubber composition according to claim 1,wherein the thiazoles in stages (Y) and (Z) is 2-mercaptobenzothiazole,di-2-benzothiazolyl disulfide and combinations thereof.
 17. The processfor producing a rubber composition according to claim 1, wherein, instage (Y), the thiurams are tetrakis(2-ethylhexyl)thiuram disulfide,tetrabenzylthiuram disulfide and combinations thereof.
 18. The processfor producing a rubber composition according to claim 1, wherein, instage (Y), the thioureas are at least one compound selected from thegroup consisting of N,N′-diethylthiourea, trimethylthiourea,N,N′-diphenylthiourea, and N,N′-dimethylthiourea.
 19. The process forproducing a rubber composition according to claim 1, wherein, in stage(Y), the dithiocarbamates are at least one compound selected from thegroup consisting of zinc dibenzyldithiocarmamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dimethyldithiocarbamate, and copperdimethyldithiocarbamate.
 20. The process for producing a rubbercomposition according to claim 1, wherein, in stage (Y), the xanthate isa zinc isopropyl xanthate.
 21. The process for producing a rubbercomposition according to claim 1, wherein an organic acid compound (G)is added in a stage of kneading after addition of the silane couplingagent (C).
 22. The process for producing a rubber composition accordingto claim 21, wherein the organic acid compound (G) is stearic acid.